La Mezquita, Córdoba, Spain. The Great Mosque of Córdoba is truly hallowed ground. In ancient times it was the site of a Roman temple, then an early Christian church. When Cordoba became the capital of the Spanish Muslim dynasty, the mosque was founded 785 AD. Over the next 200 years it was expanded to become the third largest structure in Islam, until it was captured by Christian Spanish King Ferdinand III in the 13th century. In 1523 a cathedral was built in the center of the mosque.

What the photo doesn't show is that it is actually quite dark in here, especially when you enter from the blazing Spanish midday sun. As your eyes become adjusted to the low light, the forest of nearly 500 columns emerges, an awesome, breathtaking experience.

To really get a better feel about what it's like to be here, check out this panorama view.